Dark Matter

Most of the universe's stuff is apparently dark matter, [invisible:disappearing] material pervading the universe and supplying the bulk of the [gravitational:transparent] attraction [holding:forming] galaxy clusters [together:differently] . The matter contained in the visible stars in the cluster isn't enough to keep the clusters from flying apart.Now comes one of the [strongest:clearest] pieces of evidence for dark matter. The Hubble space [telescope:camera] has found what looks like a ghostly ring, the remnant of a massive collision between two galaxy clusters sometime in the last two billion years.The ring is about 2.6 million light years across and lies about five billion light years from earth. A Johns Hopkins research team noticed the ring. They can't directly see it, of course. But they infer its existence because its gravity bends the light of more distant galaxies in the background. One researcher was initially [annoyed:angry] with the ring because he assumed the ring was some kind of problem or error. A literature search turned up evidence of a collision between galactic clusters near the ring. And computer simulations showed that a dark matter ring would indeed result, like the ripples on a pond.